1. Field of the Invention
The present invention relates to an unvulcanized rubber member for tire manufacturing, a device for producing the unvulcanized rubber member for tire manufacturing, and a method of producing the unvulcanized rubber member.
2. Description of the Related Art
When a molded unvulcanized tire is charged into a vulcanizing mold and then vulcanized, defects referred to as “lights” may appear on the surface of a fabricated tire after vulcanization. As a result, a problem is caused in that the external appearance of the fabricated tire deteriorates and the commercial value thereof decreases. “Lights” are generally produced due to air remaining between the unvulcanized tire and the vulcanizing mold.
Further, when a molded unvulcanized tire is charged into a vulcanizing mold and then vulcanized, a defect may occur in that air remains at the interior of the fabricated tire after vulcanization. Due to this defect or air void, a problem is caused in that performance and quality of the fabricated tire are deteriorated and the commercial value of the fabricated tire is decreased. Such a defect i.e., production of air void is caused because air remains between members for structuring the tire (which members will be referred to as “tire structuring members” hereinafter), during assembling of the tire structuring members and molding of the unvulcanized tire.
Conventionally, in order to solve these problems, methods such as those described below and the like have been attempted to prevent lights from being produced on the surface of a fabricated tire and prevent air void from being formed at the interior of the fabricated tire by promoting bleeding of residual air:    (1) a plurality of vent holes for air-bleeding are provided inside a vulcanizing mold;    (2) outside coatings, which contain solid fillers for air-bleeding, are applied to the surface of an unvulcanized tire;    (3) a plurality of protrusions or grooves having predetermined size and predetermined pitch are linearly formed, in a circumferential direction of the tire, on the surface of a tire structuring member to be used at the side of the surface of the tire (as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 60-143944);    (4) a plurality of grooves having predetermined pitch and predetermined size are linearly formed, in a radial direction of the tire, on the surface of the tire structuring member to be used at a side of a surface of the tire (as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 10-67056); and    (5) air remaining between the tire structuring members is pushed out by “stitching” the members by a metal or rubber roller during assembly;
In reality, however, the conventional methods described above have caused such problems as those described below:    In the method of (1), that is, in providing a plurality of vent holes, a great deal of expense is required, a lot of spews remain on the surface of the fabricated tire after vulcanization, much time and labor is required to remove the spews, and the external appearance of the fabricated tire is damaged;    In the method of (2) of applying the outside coatings, a specific device for the application and considerable expense for coating are necessitated i.e., the coating process thereof is quite time and labor consuming;    In the method of (3) of forming linear protrusions or grooves in the tire circumferential direction, air cannot be bled efficiently from the tire surface because irregularities located along the circumferential direction of the vulcanizing mold or located along a radial direction of the unvulcanized tire hinder bleeding, by way of the linear protrusions or grooves, of the air remaining between the unvulcanized tire and the vulcanizing mold during the vulcanization of the tire;    In the method of (4) of forming linear grooves in the tire radial direction, in order to bleed the air efficiently, it is necessary to form the grooves at considerably fine pitches, whereby a large device and thus a large space are required, which is costly; and    In the method of (5), it is impossible to conduct efficient bleeding of the air remaining between the tire structuring members by roll-stitching, because most of the tire structuring members for the unvulcanized tire have high tackiness.